1. Field of the Invention
The present invention relates to a linear compressor, and more particularly, to a driving controlling apparatus for a linear compressor capable of stably varying a stroke in a large cooling capacity condition by implementing a voltage control mode at the time of an overload (more than a TDC), and by implementing a current control mode at the time of a normal load (less than the TDC), and a method thereof.
2. Description of the Background Art
Generally, a linear compressor reciprocates a piston with using a linear motion of a motor by directly connecting the piston to a mover of a linear motor.
When the linear compressor is applied to a compressor or a refrigerator a compression ratio of the linear compressor is varied by varying a voltage inputted to the linear compressor thus to control a cooling capacity.
FIG. 1 is a block diagram showing a driving controlling apparatus for a linear compressor in accordance with the related art.
As shown in FIG. 1, the driving controlling apparatus for a linear compressor comprises a current detecting unit 4 for detecting a current applied to a motor; a voltage detecting unit 3 for detecting a voltage applied to the motor; a stroke estimating unit 5 for estimating a stroke by the detected current, the detected voltage, and a motor parameter; a comparing unit 1 for comparing the stroke estimation value with a stroke reference value thereby outputting a difference value therebetween; and a controlling unit 2 for controlling a stroke by varying a voltage applied to the motor according to the difference value.
An operation of the related art driving controlling apparatus for a linear compressor will be explained.
The current detecting unit 4 detects a current applied to the motor, and a voltage detecting unit 3 detects a voltage applied to the motor.
The stroke estimating unit 5 calculates a stroke estimation value by using the detected current, the detected voltage, and a motor parameter. Then, the stroke estimating unit 5 applies the stroke estimation value to the comparing unit 1.
Then, the comparing unit 1 compares the stroke estimation value with the stroke command value, and applies a difference value therebetween to the controlling unit 2. Then, the controlling unit 2 varies a voltage applied to the motor thus to control a stroke.
As shown in FIG. 2, when the stroke estimation value is greater than the stroke command value, the controlling unit 2 decreases the voltage applied to the motor. On the contrary, when the stroke estimation value is smaller than the stroke command value, the controlling unit 2 increases the voltage applied to the motor.
The linear compressor obtains a stroke estimation value by using a motor parameter (α), a resistance (R), and a reactance (L), and controls the stroke by using the stroke estimation value.
The related art linear compressor using a stroke voltage controls a voltage by controlling an LC resonance with using a capacitor.
In the related art linear compressor, since the voltage applied to the motor and the stroke are in proportional to each other, it is easy to perform a TDC control and a stroke variation.
However, as shown in FIG. 3, when a voltage control is performed in the linear compressor with a removed capacitor, the voltage applied to the linear compressor is not proportional to the stroke but a stroke tremble phenomenon occurs. Accordingly, it is difficult to perform the stroke variation.
Furthermore, in the linear compressor with the removed capacitor, a driving efficiency and a reliability of the linear compressor are lowered at the time of an over-stroke occurrence due to the stroke trembling phenomenon.